Nicholas Roberts/For The Star-LedgerHackers gather to share tips of the trade at a convention in this file photo.

What looked like an innocent Christmas e-card from the White House turned out to be ploy by hackers to steal documents and other data from several law enforcement, military and government workers.

The targeted e-mail attack that surfaced just before Christmas prompted recipients to click on a link which would then download the ZueS malware — a well-known malicious code often used to steal passwords and Internet banking information.

While the attack was relatively small and targeted a limited amount people with government ties, analysts believe the hackers responsible are the same ones behind a larger attack last February when at least 74,000 computers were infected with a similar version of the ZueS malware. Analysts revealed the ZueS code can be modified slightly by hackers to bypass anti-virus software and firewalls currently in place.

One U.S. official said that the code was rather poorly written. The hackers could only get easily accessible documents and not those filed deep within layers of folders on the hard drive, said the official, who spoke on condition of anonymity to discuss ongoing investigations.

Still, the attack comes at a time when the federal government is struggling to increase its cybersecurity after the release of thousands of State Department cables and military documents by the WikiLeaks website.